The evaluation of dynamic flow pattern is helpful for the diagnosis of cerebrovascular malformations. As the gold standard, digital subtraction angiography (DSA) is invasive with exposure of x-ray to both doctors and patients. A time-resolved non-contrast 4-D MRA technique termed TrueSTAR was introduced recently by combining ASL with multi-phase segmented balanced SSFP readout, providing both high spatial and temporal resolutions¹. However, the standard TrueSTAR using Cartesian sampling (Cartesian-TrueSTAR) remains challenging to achieve both adequate imaging coverage and time frames within a clinically acceptable acquisition time. To overcome the limitations, a non-contrast 4-D MRA using stack-of-stars golden angle acquisition (Radial-TrueSTAR) has recently been introduced, which can accelerate the imaging speed up to 3 fold while preserving the spatiotemporal resolution². To improve the delineation of distal arteries, a variable flip angle (VFA) scheme³ was also applied in both TrueSTAR acquisitions. In the present study, we evaluated the clinical utilities of Cartesian- and Radial-TrueSTAR in cerebrovascular malformation patients by comparison with time-of-flight (TOF) and DSA.Seven patients with intracranial arteriovenous malformation (AVM) (43.6±11.4 years, 4 males) were enrolled in this study. Four patients had history of embolization treatment and 3 patients had radiotherapy. All the scans were performed on Siemens Tim Trio 3T scanners using product 12-channel head coil. 4-D MRA images were acquired from each patient using both Cartesian- and Radial-TrueSTAR with closely matched imaging parameters including voxel size:1.1x1.1x1.5mm³ (Cartesian) and 1x1x1.5mm³ (Radial), temporal resolution≈100ms, acquisition window=2.5s. 32 slices per slab were acquired resulting in a total scan time per slab of approximate 7 and half minutes and 3 minutes for Cartesian and radial samplings, respectively. To fully cover the draining veins, two slabs were acquired in some AVM cases using Radial-TrueSTAR, which took a similar scan time with the single-slab Cartesian-TrueSTAR. DSA was performed for follow-up. TOF images were also collected from each subject. Spetzler–Martin grading scale was evaluated with 4-D dMRA, TOF, dMRA plus TOF and DSA respectively by two neuroradiologists. Diagnostic confidence scores for three components of AVMs (feeding artery, nidus and draining vein) were graded from 1 (poor imaging quality with severe artifacts and no diagnostic value) to 5 (excellent imaging quality with no artifacts and definite diagnosis)⁴. Kendall's coefficient of concordance was calculated to evaluate the reliability between two raters within each modality (dMRA, TOF, TOF plus dMRA). The Wilcoxon signed-rank test was applied to compare the diagnostic confidence scores between each pair of the three modalities for each component of an AVM, respectively. Lesions were detected in 5/7 patients on DSA (Table 1). The delineation of AVM lesions using TrueSTAR is consistent with that of DSA, except dMRA failed to detect one small lesion (6mm) with low blood flow which was manifested as lightly stained on DSA. DMRA had the same Spetzler–Martin grading scales in terms of AVM size and location but failed to detect deep draining veins in 2 patients. The dynamic fillings of labeled blood through feeding arteries, nidus and draining veins are clearly visualized in AVM (Figure 1). Compared to Cartesian-TrueSTAR, Radial-TrueSTAR offers larger spatial coverage under the similar scan time, which shows better delineation of draining veins, as shown in Figure 1. Furthermore, Radial-TrueSTAR performs better than Cartesian-TrueSTAR (Table 2) due to better background suppression, although there is no statistical significance (p>0.05) achieved due to the small sample size (4 cases). On the other hand, compared to TOF, the heterogeneity within the nidus can be observed using both Cartesian- and Radial-TrueSTAR (Figure 1). Therefore, although TOF depicts details of feeding artery better, it has lower diagnostic confidence scores in terms of nidus compared to TrueSTAR. Improved diagnostic accuracy was achieved when dMRA and TOF MRA are combined (Table2). Our preliminary study demonstrates the feasibility of both Cartesian- and Radial-TrueSTAR for the evaluation of hemodynamics in cerebrovascular malformations. TrueSTAR can provide complementary temporal information to TOF and shows better depiction of nidus than TOF. TrueSTAR combined with TOF can enhance diagnostic confidence. However, TrueSTAR remains challenging to detect small lesions. Compared to Cartesian-TrueSTAR, Radial-TrueSTAR provides the shorter scan time while preserving the similar image qualities. Therefore, Radial-TrueSTAR may become a promising approach with reduced scan time and patient comfort in clinical applications. Further evaluations are required to determine the clinical efficacy of Radial-TrueSTAR in a large patient population.